Recent research and updated expert guidelines for exercise during pregnancy and the postpartum period enthusiastically promote physical activity for its overall health and fitness benefits. Weight gain and hormones of pregnancy cause anatomical and physiological adaptations that affect both mother and fetus at rest and during exercise. The possibility of musculoskeletal discomfort or injury during exercise requires implementation of a prudent exercise prescription properly designed and lead by an experienced fitness professional in consult with the obstetrician. Profound hemodynamic changes help meet the demands of both the mother and growing fetus by assuring adequate circulation of oxygen and nutrients to the uterus during exercise while facilitating dissipation of an increased heat load. Changes in the respiratory system increase the volume of air breathed and more efficient gas exchange enhances oxygen availability to and carbon dioxide removal from the fetus. Fuel metabolism is altered with an increased demand for carbohydrate during exercise. Adequate intake of food to meet energy needs without excess calorie consumption resulting in unwanted weight gain and obesity requires careful monitoring. Redistribution of blood flow from the uterus to exercising muscles presents a hypothetical risk but there is no evidence of adverse pregnancy outcomes. The exercise prescription needs to be individualized and formulated with specific goals in mind. It should be determined if the woman desires only the achievement of overall health and fitness objectives, or if she wishes to pursue recreational activities and/or competitive sports. A comprehensive program includes cardiovascular, musculoskeletal and core stability training with the intensity and volume of exercise varied based on the goals and ongoing health status of each woman and her developing fetus as the pregnancy progresses. We conclude that physical activity during pregnancy has minimal risks and many potential benefits. Therefore, restrictions on exercising should only be indicated if warranted by obstetric/medical determination.